Cardiac arrhythmia, or a disruption in the normal heartbeat rhythm, is a prevalent condition, causing more than 850,000 people to be hospitalized in the United States each year. There are several types of cardiac arrhythmia, including tachycardia (resulting in an abnormally fast heart rate), bradycardia/bradyarrhythmia (resulting in an abnormally slow heart rate), supraventricular arrhythmias (arrhythmias that originate in the atria), and ventricular arrhythmias (arrhythmias that originate in the ventricles).
There are several ways in which arrhythmias may be treated, one of which being catheter ablation, which may be an effective treatment for cardiac arrhythmia. However, there are difficulties associated with many of the commonly used procedures. For example, linear or spot ablation may be desired to treat a particular arrhythmogenic focus. In such a case, a focal catheter may be used. This catheter, or first a delivery sheath, is typically passed through the patient's vasculature into the heart to reach the target treatment site. In order to safely navigate through the tortuous vasculature pathways, the catheter and/or sheath must be highly flexible or steerable. However, in the case of focal catheters, the catheter must also be rigid enough to hold its shape without collapsing when pressed against the target tissue to make the ablation lesion.
Additionally, some aberrant electrical signals may originate from within one or more pulmonary veins, the ostia to which are located in the left atrium. Typical access to the left atrium includes a vascular pathway into the right atrium, through the septum, and into the left atrium. However, accessing the pulmonary veins once inside the left atrium may require difficult and precise steering of the catheter and/or sheath to reach the target treatment site. Some catheter designs include a portion of the elongate body including one or more bellows or accordion-like pleated areas, but these pleated areas do not lend rigidity to the catheter as well as flexibility, and the shape of the catheter must be maintained during treatment by internal rods, pull wires, or other means such as tensioning devices. Such means may significantly reduce the diameter of an inner lumen of the catheter, and are therefore unusable in over-the-wire catheters. Further, such configurations are unusable in guide sheaths, because the diameter of an inner lumen would not be sufficient to accommodate a treatment device therethrough.
Therefore, it is desired to provide a system and device that is easily navigated through the patient's vasculature into the heart but rigid enough to exert pressure against the target tissue, and that may be transitioned from a flexible state to a rigid or semi-rigid state without the need for internal rods, pull wires, tensioning devices, or other means.